Steroids, particularly 5.alpha.-steroids and their 4,5 and 6,7 dehydro analogs, are a well known class of chemical compounds, many members of which are well known for their physiological activity. Steroids with a keto group at the 3-position are especially useful. In the androstane series, 5.alpha.-steroids are utilized as anabolic agents and fertility control drugs and for the preparation of these useful compounds. Certain steroids in the pregnane series are particularly effective as anti-inflammatory agents and as cardenolides. Representative steroids in the cholestane series including cholesterol and sitosterols, particularly .beta.-sitosterol, are naturally occurring, and are candidates as starting materials for the commercial preparation of therapeutically useful steroids.
Steroids with a wide variety of substituents on the molecule have proved to be useful for therapeutic purposes. For example, in the pregnane series, 11.beta.-hydroxyl, 6.alpha.-fluoro and 6.alpha.-chloro substituted compounds having a 9.alpha.-fluoro substituent are described as having corticoid activity, and in some cases diuretic activity [see JACS 81, 3156 (1959); JACS 82,3399 (1960); JACS 80, 6464 (1958); U.S. Pat. No. 2,864,836 and U.S. Pat. No. 2,838,547]. In the androstane series, 11.beta.-hydroxyl substituted compounds are described as having antiandrogenic and gonadotropic activity (See U.S. Pat. Nos. 2,731,479 and 2,702,811). Those skilled in this art will be well aware of other variations of the basic steroid nucleus which can be utilized to provide useful compounds.
Many synthetic procedures are available for the production of useful steroids from naturally occurring steroids. Diosgenin is an important source of steroids of the pregnane series such as prednisolone and its numerous derivatives. Because of their ready availability from plant sources, sitosterols, particularly .beta.-sitosterol, have been the subject of many studies to adapt them as commercially useful starting materials for 5.alpha.-steroids of the pregnane and androstane series. These studies have not met with significant success. The principal reasons have been the difficulty in removing the side chain, except in low yield, and the difficulty in introducing functional groups into a molecule which is devoid of such groups, except for the 3.beta.-hydroxyl group and the double bond at the 5,6 position.
The available methods for removing the side chain are by either chemical or microbiological oxidation. The yields from each of these procedures are undesirably low. Moreover, the capital investment required to construct, operate and maintain a plant for a microbiological oxidation is very significant.
For these and other reasons well known to those skilled in the art, there have been continuing efforts to devise novel methods for the production of useful steroids